Millions of retired Americans are frozen out of the health care system even though they've paid into it all their lives, because most of them rely on Social Security for the bulk of their income and can't afford the 20 percent of every medical bill that Medicare requires them to pay.

These numbers will grow enormously over the next 15 years as the population ages, whatever our economic future. Fundamental shifts in employment and incomes growing out of what's still being called the Great Recession will likely compound the problem for decades.

And demographic and other statistics strongly suggest that this is only the beginning of an unavoidable challenge to the idea of what it means to grow old in America, and to what many consider the obligations of government to citizens. In this pass, the political system seems unable to even concede the facts, much less design a practical response to them.